Hi! Throughout my musical education, I was instructed with Simmandl's two methods and etudes (my teacher is very fond of Simmandl's approach to bass playing). But now I wish to explore new options and, looking into it, two names have appeared at sight: Billè and Rabbath. I have found (from this Forum) more or less some information about Rabbath's Nouvelle Technique, whereas of Billè's methods I know nothing. Can some kind soul instruct me on the differences between these three schools?